在servlet中生成验证码
package login;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.Random;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;
/**
* 生成验证码servlet
* @author Administrator
*
*/
public class CheckCodeServlet extends HttpServlet {
public void service(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
System.out.println("service called");
/**1.设置server响应类型为jpg格式图片 */
response.setContentType("image/jpeg");
/**2.绘图**/
//1.在内存中开辟空间存储图片
BufferedImage image = new BufferedImage(60,25,BufferedImage.TYPE_INT_RGB);
//2.获得画笔
Graphics g = image.getGraphics();
//3.准备随机数对象
Random r = new Random();
//4.设置图片背景色
g.setColor(new Color(r.nextInt(255),r.nextInt(255),r.nextInt(255)));
//5.填充
g.fillRect(0, 0, 60, 25);
//6.设置画笔前景色(设置字体颜色)
g.setColor(new Color(0,0,0));
//7.产生随机数
String number = String.valueOf(r.nextInt(99999)+1000);
/**将验证码存放session中*/
HttpSession session =request.getSession();
session.setAttribute("checkcode", number);
//8.数字画到图片上
g.drawString(number, 15,15);
g.drawLine(r.nextInt(20), r.nextInt(20), r.nextInt(50), r.nextInt(50));
g.drawLine(r.nextInt(20), r.nextInt(20), r.nextInt(50), r.nextInt(50));
g.drawLine(r.nextInt(20), r.nextInt(20), r.nextInt(50), r.nextInt(50));
g.drawLine(r.nextInt(20), r.nextInt(20), r.nextInt(50), r.nextInt(50));
/**3.使用特定格式压缩图片并输出*/
//1.建立文件输出流
OutputStream os =response.getOutputStream();
//2.使用指定格式
JPEGImageEncoder encoder =JPEGCodec.createJPEGEncoder(os);
encoder.encode(image);
}
}
在jsp页面使用java产生的验证码：
<td style="width:80px">
验证码:
</td>
<td valign="middle" >
<input name="validatecode" size="7px"/>
<img src="checkcode" id="img"><!-- 等效于"#" -->
<a href="javascript:;" onclick="document.getElementById('img').
src='checkcode?'+new Date().getTime();"><span style="font-size:12px;">看不清。换一张</span></a>
<br/>
<span style="color:red;">
<%
String check_error=(String)request.getAttribute("check_error");
%>
<%=check_error==null?"":check_error%>
</span>
</td>
在xmd文件中面的配置
<servlet>
<servlet-name>check</servlet-name>
<servlet-class>login.CheckCodeServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>check</servlet-name>
<url-pattern>/checkcode</url-pattern>
</servlet-mapping>
进行验证推断的部分代码：
String validatecode=request.getParameter("validatecode");//验证码
String checkCode=(String)session.getAttribute("checkcode");
在servlet里面进行比較